1. Field of the Invention
The present invention relates to a method and apparatus used in an adhesion process for adhering laminated glass (safety glass) such as a windshield of a vehicle.
2. Description of the Prior Art
In a conventional windshield of a vehicle, a plurality of sheets of plate glass are adhered together through a plastic film such as a polyvinyl butyral film to prepare so-called safety glass. Such laminated glass is prepared such that adhesion interlayers are inserted between the plastic film and the sheets of plate glass and are preliminarily adhered thereto. The resultant structure is finally pressed in an autoclave. The preliminary adhesion is performed to remove bubbles, water content and residual steam from the adhesion layers. In principle, an apparatus is used wherein the laminated glass is passed through a pair of press rolls.
According to the most basic press roll apparatus, a pair of press rolls are vertically disposed, and a worker at the insertion side inserts laminated glass into the pair of press rolls and another worker at the exhaustion side picks it up from the pair of press rolls. This apparatus has disadvantages in that the operation requires much labor and a uniform pressure cannot be obtained when the laminated glass has a complicated three-dimensional surface.
A conventional automatic press roll apparatus has been used to automatically perform the preliminary adhesion process for a three-dimensional glass surface. According to this press roll apparatus, each of the pair of press rolls is divided into a plurality of annular segments. Some of the roll segments can then be inclined in accordance with the curved surface of the laminated glass. In addition, all the roll segments are supported by a rotational frame. When the glass passes between the press rolls, the rotational frame swings in accordance with the curved surface of the glass so as to apply a constant press pressure to the glass surface in the direction perpendicular to the glass surface. This conventional automatic press roll apparatus also has a counterbalance mechanism for cancelling the weights of the press rolls so as to obtain a constant press pressure when the rotational frame swings and the pressure application direction is inclined with respect to the vertical direction (the direction of gravity).
This press roll apparatus is effective for automatically pressing the laminated glass having a relatively simple three-dimensional surface. However, the rotational frame and the counterbalance mechanism are driven by a guide cam corresponding to each three-dimensional surface. The guide cam must be replaced with another guide cam corresponding to the surface of the windshield in accordance with the type of vehicle. Therefore, this conventional press roll apparatus is not suitable for mass production of different types of windshield.